1. Field of the Invention
The present invention relates to a mobile communication system, a hand over controller, and a hand over controlling method.
2. Description of the Related Art
In recent years, there has been proposed a method of implementing a “high-quality handover control” by expanding the Mobile IPv6 (see D. Johnson, C. Perkins, and J. Arkko, “Mobility Support in IPv6”, RFC3775, June, 2004, for example) as a typical protocol providing a mobility on the Internet based upon the IETF (Internet Engineering Task Force). Such a high-quality handover control is realized by, for example, the Hierarchical Mobile IPv6 (HMIP) in which a node called a mobility anchor point (MAP) is introduced into a mobile communication system to shorten a location registration period (see H. Soliman, C. Catelluccia, K. E L Malki, and L. Bellier, “Hierarchical Mobile IPv6 mobility management (HMIPv6)”, Internet Draft: draft-ietf-mipshop-hmipv6-02.txt, June, 2004, for example).
However, in a conventional mobile communication system, one high-quality handover control system is employed in one packet transfer network. Therefore, the packet transfer network accessed by a mobile node is not always capable of handover control meeting a service quality desired by the mobile node or a service quality commensurate with traffic.
For example, in some cases, once the mobile node is moved to a packet transfer network that makes a handover control different from a desired one, the mobile node cannot receive a high-quality handover control. To be specific, as shown in FIG. 1, when a mobile node requiring a fast handover accesses a packet transfer network that gives a handover control suitable for preventing a packet loss, the service quality desired by the mobile node is not always guaranteed. In contrast, when a mobile node requiring reduction in packet loss accesses a packet transfer network that gives a fast handover control, the service quality desired by the mobile node is not always guaranteed.